The most common and most likely answer to this crossword clue is the 6 plus 9 letter word DOLLAR DIPLOMACY
I've seen this crossword clue in The Guardian
D
O
L
L
A
R
D
I
P
L
O
M
A
C
Y
Buddy explains!
The straight part
We know that "where finance dictates policy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case where finance dictates policy = dollar diplomacy.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.